Understanding what makes an effective teacher, as well as how teachers sort by their effectiveness across schools, is central to understanding and addressing student achievement gaps. Prior studies have found substantial sorting of teachers across schools, with the schools with the highest proportions of poor, non-white, and low-scoring students…

Arguably the most important educational resource is teachers. Teachers and teaching quality are a central feature of the No Child Left Behind Act of 2001 (NCLB) which requires a "highly qualified teacher" in every core academic classroom. Many states and large districts also have policies in place to attract qualified teachers to…